Les Cahiers de prothese最新文献

In subtotal mandibular edentations, the roots of remaining anterior teeth might be used to enhance the retention of a full denture in building a contramucosal retention bar. Based on a case-report, the authors present the fabrication in five clinical and laboratory sequences, of a maxillary full denture combined with a lower full denture and a retainer bar joining two cuspids. First sequence: Clinical. It mainly concerns: 1) Preparation and impression of the two cuspids for receiving the two posts on which the retention bar will be fixed. 2) The primary plaster impression of the soft tissues. In the laboratory, the coping are directly cast with gold without a core, topped with resin. The individual mandibular impression tray (IIT) presents two windows opposite the two preparations through which the tops of the two copings are showing. Second sequence: Clinical. If the maxillary impression is a classical one, the mandibular impression is peculiar and original. Overall, this provides a reliable working model on which the dental technician will be able to build, the entire prosthesis, not only the retainer bar but also the full denture. This is done in two stages: 1) Secondary impression of the soft tissues with copings in place. 2) Indexing of the copings to the impression tray with acrylic resin, pressing firmly on the rims of the IIT and simultaneously, on the tops of the copings to take into account the different depression of the tissues. In the laboratory, both impressions are boxed and cast, with in place.(ABSTRACT TRUNCATED AT 250 WORDS)

Unscaling a fixed prosthesis can be dangerous for the supporting tissue. However a careful examination of the clinical situation and the proper use of correct technics described in the following article, may prudence a successful result most of the time.

The authors propose a study of the surface energy of dental resins. The two liquids measure method, by means of water and alkanes enables to determine the dispersive and polar components of this energy and therefore to understand what types of bindings may be altered in the process of various physical or chemical treatments of the surface of the material. Treatment by alcoholic potash, or immersion of the resin in water, increase the polar component of surface energy by inducing a re-orientation of polymer molecules along the interface between P.M.M.A. and water. This improvement is not reversible. It reaches its maximum towards the eighth day of immersion in water. It cannot be obtained in saliva, a feebly polar medium. After a temporary increase towards the third day, the dispersive component of surface energy falls back approximately to its initial value. This treated resin can no longer be considered as a low energy solid. All comparative experimentation on the surface energy of prosthetic materials ought to be made on resin treated by water immersion.

Feldspatic porcelains are usually material in cosmetic dentistry, but they cannot be used without a reinforcement system. Aluminous or metallic frames produce a strong internal specular reflexion, which destroys the deep natural appearance of teeth. Inspired from glass ceramic industry, the concept of strengthening in Optec hsp is induced by a high level of micro-crystalline dispersion, spread in the material. Micro-crystals increase strength by division of stresses and improve the scattering of light as we observe in the natural tooth. The laboratory method is based on routine technics of porcelain building. No special equipment, or high temperature are necessary for producing, laminate veneers, inlays, onlays, crowns, and tree units anterior bridges.

Replacement of a missing incisor with an osseo-integrated implant, presents a difficult prosthetic problem for the practitioner because of the obliqueness of the implant and its diameter smaller than the tooth to be reconstructed. Therefore, a topographic and aesthetic pre-estimation is highly desirable. The patient whose treatment is described hereafter, presents large diastemas permitting to set the missing tooth in several locations. The various options are simulated on a study model and recorded by a silicone or resin index. This index is cut out so that the implant site is clearly defined and it presents a guide rod indicating the direction of the alveolar bone. The optimal site is selected during the surgical procedure with the most favorable index depending on the residual bone. After the implant is released, the location impression, is taken using asymmetric transfer allowing a strict positioning of the implant's replica and its thread. In order to prevent the making of a triangular-shaped crown, a false transfixed core removable is built over the intramobile component of the IMZ as well as pa periodontal ring. The latter is independent and maintained by the intramobile component. It compensates the difference in diameter between the implant and the natural tooth to be reconstructed. Its finely polished but asymmetric internal aspect prevents the rotation of the device. The volume of this device is controlled by a silicone index made on the preestimation model. Both pieces are cast in gold and assembled on the implant with a positioning indes. Parallel proximal grooves increase the friction of the core and a ceramo-metal crown is built in the conventional fashion. It is temporally cemented, and periodically removed and cleansed. The absence of gingical sulcus provides an aesthetic result similar to a bridge component.

Some clinical observations have brought the authors to suspect a corrosion of acrylic resins by an alcaline peroxide (Steradent) proposed as a denture cleanser. By way of a laboratory simulation they have shown that standardized samples of Lucitone 199 are corroded by the main active agents issuing from Steradent: oxygen and a high level of alcalinity. A daily use of Steradent can thus badly affect the physical properties of denture acrylic bases.

An increased pneumatization of the maxillary sinus and an important alveolar crest resorption usually means a contra-indication to any endosteal implantation unless a grafting of the maxillary sinus is attempted. As early as 1986, a scanner analysis was performed over 200 patients to scrutinize a new anatomical approach of the tubero-pterygoid junction. The maxillary bone, especially the tuberosity is extremely spongious and fragile. On the other side the tubero-pterygoid junction at the boundary of the palatal bone and the two pterygoid wings presents a limited site but essentially cortical, very secure to assure the primary stability of a Brånemark implant. The scanner X-ray enhances the tubero-pterygoid junction and allows to reposition it in the three planes. It mainly consists of superimpositions of computerized coronal and axial tomographs. The scanner computer is providing the right pathway from the tuberosity to the pterygoid process.

Some confusion exists in the anatomical description of the mandibular retromolar area. The anatomical terms of retromolar area, papilla, tubercle, trigone, triangle, fossa, dimple, are often confused in the literature. This article specifies the terminology as well as the anatomical organization of this area, the use of which in prosthodontics is the subject of scholastic discussions, in full dentures. This clinical examination based on a precise anatomical knowledge, will determine the participation of the support area and its structures bordering this area. Compression of the lingual nerve by the base of the prosthesis in his area, must always be considered as a possible etiology, pain complain involving the territory of this nerve.

"Electromyographic biofeedback", or biological retroaction, used as a training process, concerns numerous medical specialties, and in a wider sense, to dentistry. Based on several studies, this article explains the various indications of this method in our discipline, stressing particularly the effect of electromyographic biofeedback in the treatment of cranio-mandibular disorders, emphasizing the different modes of application (in-patient or ambulatory). Acting at two levels, stress reduction and inducing relaxation of contracted muscles, electromyographic biofeedback occupies an excellent place in everyday practice. Finally, considering the results of their own study, of the particular type of relation instituted by the treatment and its role in the care and monitoring of the patient, the authors emphasize a major indication: the treatment of cranio-mandibular disorders of non-organic origin.

This technique permits the preparation of ceramic jacket crowns made on Sunrise laminated precious metal alloy. The Sunrise foil is gold-colored, made of 99% of precious metals and is 50 microns thick. The die is prepared in order to display a moderate and regular undercut beyond the cervical limit. The margin will be underlined with a red pencil. The Sunrise foil is cut according to predetermined templates. Then the foil is applied without burnishing, according to the technique of jacket crowns on platinum foil only by finger pressure. The double folding on closure is preferably done distally or mesially. Then, the metal base is disinserted, sandblasted with 100 microns aluminum oxide, replaced on its die, and placed in a rubber casing before being placed in the isostatic press, to be subjected to a pressure of 2,000 TSI (14 kg par cm2). Sunrise's orange color reinforces rather subtetly the overall color, making these reconstructions particularly esthetic. The color of the Sunrise metal does not require, therefore a too thick opaque. Any ceramic intended to be fired on a metal base, may be used in respecting its firing protocol. Sunrise, as any other technique of this type, require a careful preparation with a shoulder that has a rounded gingivoaxial line angle. Bridges may be built on the "thimbles" crowns, fitted on Sunrise cores, the pontics being made as a ceramo-metal framework.